Tehebratula. MOLLUSCA. ACEPHALA. 371 



convex ; front defined by two angles, or emarginate ; edge becoming blunt 

 by age, — Soiver. Min. Conch, t. ccccxxxv. f. 5 — Upper Oolite. 



27. T. globata. — Subglobose ; front elevated with two obtuse folds, and 

 slightly produced ; surface often minutely punctated — Soivcr. Min. Conch, 

 t. ccccxxxvi. f. 1 Upper Oolite. 



28. T. perovalis. — Ovate, convex, with two elevated sinuses at the front, 

 which is depressed between them ; beak incurved — Soiver. Min. Conch, t. 

 ccccxxxvi. f. 2, 8. — Under Oolite. 



29. T. maxillata. — Subqiiadrangular, convex ; two acute rising sinuses in 

 the front, and one obtuse sinus on each side ; three conspicuous furrows in 



the upper, and two in the lower valve ; front rounded Sower. Min. Conch. 



t. ccccxxxvi. f, 4. — Upper Oolite. 



30. T. Sella — Subqiiadrangular, convex ; front considerably elevated, nar- 

 row, emarginated when old ; sides depressed, slightly roinided — Sower. Min. 

 Conch, t. ccccxxxvii. f. 1. — Upper Oolite. 



31. T. ohtusa — Suborbicular, rather depressed ; front broad, elevated ; 

 edge obtuse. — Sower. Min. Conch, t. ccccxxxvii. f. 4.0— From Camlridyc. 



32. T. obesa — Ovate, gibbose, front elevated considerably, with a slight 

 broad sinus in the middle ; beaked valve regularly convex to the edge ; beak 

 incurved, short Soiver. Min. Conch, t. ccccxxxviii. f. 1. — In Chalk. 



33. T. bucculenta. — Rather square, with rounded sides, convex ; front pro* 

 duced, truncated, very slightly elevated ; beak short — Sower. Min. Conch, 

 t. ccccxxxviii. f. 2. — In Green Sand. 



34. T. triquetra — Suborbicular, Avith a produced incurved beak ; valves 

 equally convex; front slightly indented; beak obtusely keel-shaped, with a 

 carina on each side. — Sovjer. Min. Conch, t. ccccxiv. f. 1 — In Oolite. 



35. T. indentata. — Elliptical, smooth, more or less gibbose ; valves equally 

 convex ; front deeply notched ; beak small, much incurved — Sower. Min. 

 Conch, t. ccccxiv. f. 2. — In Limestone at Banbury. 



3G. T, Sacculus. — Obovate, gibbose, with a longitudinal groove along the 



larger valve ; the smaller valve slightly grooved ; front emarginate Anomia 



liEvis, Ure^s Ruth. 31,3. t. xvi. f. 9. — A sacculus, Martin''s Derb. t. xlvi. f. 1, 2. 

 — Ter. Sacc. Sower. Min. Concha t. ccccxlvi. f. 1. — In Carboniferous Limestone. 



37- T. hastata, — Elliptical, subrhomboidal, rather depressed ; front trim- 

 cated and indented; edges sharp.— .S'owct-. Min. Conch, t. ccccxlvi. f. 2, 3. — 

 Greywacke Limestone, Cork. 



38. T. cormita. — Short, convex, with blimt edges, four-lobed ; the two 

 middle lobes produced ; the others very short. — Sower. Min. Conch, ccccxlvi. 

 f 4.— In Oolite. 



39. T. amUgua — Subpentangular, gibbose, perforated valve with a broad 

 mesial groove, with a mesial ridge, having a shallow central furrow enlarging 

 at the margin— Spirifer ambiguus, Sower. Min. Conch, t. 37C — Carboniferous 

 Limestone. 



** Margin of the valves dovetailed. 



40. T. lateralis. — Oval, broader than long, gibbous ; middle of the front 

 much elevated, with three deep but short plaits ; sides with two plaits each, 

 much below the middle. — Sower. Min. Conch, t. Ixxxiii. f. 1.— In Carbonife- 

 rous Limestone. 



41. T. cm?nen«.».Deltoid, gibbous, plaited; middle of the front elevated, 



A aS 



